1. Field of the Invention
This invention relates to a mechanical seal, especially to a mechanical seal which prevents leakage of sealed fluid when a sealed fluid pressure changes and fluctuation of pressure difference take places and further prevents the occurrence of floating failure of a seal ring caused by deposition and adherence of crystals or accumulation of scales at a seal portion.
2. Description of Related Art
In a conventional mechanical seal, there has been provided a groove for mounting a seal packing (o-ring and the like as a secondary seal) and also provided a small gap between a sealing face and the opening end of the groove. Where a sealed fluid (hereinafter referred to as fluid A) contains solid substances or the fluid tends to separate out crystals, solid deposits tend to adhere to the small gap, and as a result the seal ring fails and leakage of the sealed fluid occurs, resulting in a very short life of the mechanical seal.
Accordingly, a mechanical seal is not used for a fluid containing crystals or solid substances which adhere to a seal ring, or otherwise a mechanical seal is used while flushing the sealing portion constantly with clean fluid.
Furthermore, a balance factor can be established freely with respect to a fluid pressure of fluid A located on one side of the sealing face, while a balance factor with respect to a fluid pressure of an opposing fluid (hereinafter referred to as fluid B) shall be designed in a limited range which is determined with regard to the balance factor of fluid A and a diameter of a seal packing. It is therefore an object of the present invention to provide a novel mechanical seal so that a balance factor of a mechanical seal can be easily established depending on the fluctuation of sealing pressure and to enhance the capability of the mechanical seal.